Yo guys.
I played more PC single player infected Demo.
Tired of the AI "breezing" through the chapters...before I switched over to Infected I put it on Expert. I finally got to be the ultimate dick in L4D2.
On Chapter 2. I started getting Tanks. Now this may be a demo thing but when the Tank incapped a survivor I lost control momentarily and he roared at the survivors, during this time the survivors UNLOADED into me. So note, if you get Tank. Your infected buddies are going to be much more important...assuming this ISN'T just a Demo thing.
Also...I've started discovering infected ladders, in chapter 1...Rooftop smoker, good hunter spots...and the thing is Smoker can basically go rooftop hopping to catch up survivors so no, Smoker is far...FAR from useless. The first attack possible to coordinate which is RIGHT outside the safe room door of Chapter 2, is a fucking death trap since infected can spawn from the last area(rooftop smokers, high damage hunter pounces, through the fence boomer/spitter, or around the corner spitter/boomer, around the corner charger, and behind car Jockey.)